Hydraulic system



May 11, '1948; A, R, STONE y 2,441,339

HYDRAULI C SYSTEM Filed May 17, 1945' 2 Sheets-Sheet 1 \1\ g E V) r/PArK//YGV/ZLaf/e rau/f ma l* l W Iii@ nl "-'JE A 1.1M /v I eo emmerde/HCE 5 sEco/vmer 00F/c5 63 2 e PEM/#enana cof/mous@ REL/EF mw oo'o OPE/mmHg co/vreoL #Af/vom 14A l zzgz;

U 15 lu| ALBERT RIVINGTON STONE HIS @www May ll, 1948. A. R. STONE HYDRAULIC sYsT'EM Filed May 1'7, 1945 2 Sheets-Sheet 2 mem MAX 4 WAY VALVES OPEN LEFT. MAX

4 wAY vALvEs OPEN TO ROTATE MOTORS CLOCKVIISE TO ROTATE MOTORS OOUNTERCLOCKVIISE OPERATING HANDLE sTAYs CONSTANT) n ALaEnr Rwmsrou sToNs w QWT l ms @www Patented May 11, 1948 UNITED sTATEs PATENT OFFICE HYDRAULIC SYSTEM Albert Rivington Stone, Anneslie, Md. Application May 17, 1945, Serial No. 594,279

9 claims. (ci. eso- 97) My invention relates to multiple hydraulic power units, and particularly concerns the control of such units under widely varying load demands when a constant speed, constant output source of pressure uid is employed as the energizing means. i'

An object of my invention is to provide a controlled supply system for variable-load hydraulic multiple motors, which system is compact, 'selfcontained, highly eiiicient an-d rugged. and which permits sensitive and accurate control of the motor at all times, under the most dicult and exacting operating conditions, which is of lowirst cost and which is entirely reliable under all' 'e'xtremes of operating conditions, even when handled by inexperienced operators.

Another object is to provide a system of the general type described, wherein is employed a constant speed, constant output hydraulic motor and wherein extreme flexibility of operation "can be achieved at all times.

Other-objects will in part be obvious and in part pointed out hereinafter, during the course of the following description.

My invention accordingly consists of the several parts, elements, and features of construction, and in the several operational steps, as well as in the relation of each of the same to one or more of the others, the scope of the application of all of which is set forth inthe claims at the end of this specication.

In the drawings, wherein is disclosed one embodiment of my invention which I prefer at present,

Figure 1 comprises a schematic perspective view of the entire assembly;

Figure 2 is a fragmentary view of the mode and effect of throwing the control handle; while Figure 3 is a graph showing the output shaft speed plotted against the oil flow through the system.

As conducive to a more thorough understanding of my invention, it may be noted at this time that considerable work has been directed towards the design of highly flexible hydraulic motor systems of small compass and low rst cost. It has long been realized that in general, hydraulic systems are highly desirable for a variety of variable load uses, because of the high degree of flexibility inherent therein, their non-stalling characteristics under Wide extremes of usage, and their inherent ruggedness even when subjected to considerable abuse and mishandling. Even greater flexibility is achieved where paired motors are employed, each of diierent *Y characteristics, one being adapted, to illustrate, for low-speed, high-torque duty, and the other for high speed, low-torque service. In a companion application entitled Hydraulic motor, filed June 15, 1945, Serial No. 599,679 (now abandoned), I have disclosed a multiple motor unit of this general type in which the drive components of the two motors are combined and impressed upon a common take off shaft. Such construction is not, however, essential to the proper operation of my present invention, and it is suiiicient that two hydraulic motors be energized by such system, of either like or dissimilar characteristics.

Motors of this type, as just indicated, have wide iields of application. The recent technical advances brought about by the present World War have given rise to vastly broadened horizons in widely diversified iields of application. In turret controls on ships, tanks, etc., to illustrate, and particularly in land tanks, where the vehicles are moving rapidly over terrain which changes both in general and immediate contour throughout substantially the entire progress of the vehicle, a ilexible motor control is required. It is further required that not only the motor, but as well, the energizing means and the control means be of small compass. As well, from a practical standpoint, they must be rugged and comparatively inexpensive both in first cost and in maintenance requirements.

At first thought, the simplest and most direct procedure would appear to be to provide some sort of variable output hydraulic pump connected directly to the multiple motors and supplying just the quantity of propelling fluid as is demanded from moment to moment. Diiculty is encountered, however, in that an adjustable output hydraulic pump of the type suggested is highly complicated and cumbersome, delicate, and necessarily expensive. Both in space requirements and in maintenance demands and its unreliability in the fiel-d, such a supplying unit is entirely impractical for mobile installations.

After considerable study directed to this problem, the thought occurred that perhaps satisfactory results could be obtained by utilizing the comparatively simple constant-speed, constantoutput hydraulic pump of the non-pulsating,

.preferably rotary type, and to employ therefor asimple and rugged, self-contained control system which would meter required quantities of the fluid output of the pump to the associated motors in exact accordance with the instantaneous load requirements of the said motors.

Essentially, my new system comprises a con-` constant-output hydraulic' pump,

stant-speed, and paired hydraulic motors, of either like or dissimilar characteristics, connectedvto each other across a suitable control unit including relief valves and metering valves.

lpcsedside-bv side on a suitable operating panel Both the relief valves and the metering 'valves which constitute part of my control system, and both of which will later be describedin substanf.

tially` greater detail, are housed'in .a casing ,Ic

common to them, and whichmay bef of any suitableshape anddimensions., This casing, is gen1 erally elongated and rectangular in section. I

provide a cam shaft ii extending longitudinally f through casing ,iii nearthe bottom'thereof. This cam shaft is adapted for manualV setting. The degree of movement thereof isA relatively slow and slight, yet sensitive. To this end, .itis im*- portant to mount the. cam shaft in free 4acting bearings.

l0 1 near opposite longitudinal ends thereof. These bearings may be of conventional antifriction type, and it is entirely satisfactory that they be ordinary simple journal bearings, provided only` that the shaft il: can rotate therein without appreciable binding and without appreciable resistance at the rst application of rotational force.

Before discussing ingreater-detail the features of construction of the severalvalves tandtheir precise relation one to `the other, itV will first be helpful to examine the system iinits'entirety.

An oil reservoir i3 is provided at any desired point in the system. Physically, thisv mayA be in the same compartment or 4chamber as-the rest'v of the equipment, or it may beplaced in a separate compartment. It may be open or closed, as desired. While shown vas open-convenience and caution dictate that in actual practice, this reservoir should be closedto prevent the influx into the system of Water, dust or debris. Ahy.- draulic pump It is provided,i associated .with reservoir I3 by asuitable suction pipe 14A..

An extremely important feature of my, invenrating. From pump I4, an outlet pressure lead I5 extends to the casing IQ.

Since variable load conditions exist, it isfnec--vr essary that control means be interposed :between 1 the pump l and the variable iload'which will.

Any suitable bearings may be used, and these are illustrated .as comprised bysuitable straps or carriers I2, i2 made fast to the casing It is entirely feasible howl' 4 later be described. It is the controls within casing Il) which serve to fulfill this requirement. It is, of course, possible to install a pump of output which varies in accordance with the load requirements. Such a pump, however, as has been suggested, is both cumbersome and costly, and thus is highly impractical. I have evolved the present compact control assembly as a solution to this difficulty.

Fort'he operation oflthe tank'turret or other object to beenergized bythe two motors, I provide a low-speed, high-torque, heavy-duty motor IS known as a tracking motor, and a comparativelyhigh-speed, low-torque motor il, which for convenience I term a slewing motor, disi8, all of which is shown schematically at the lower right of the figure. In a convenient and typical design the tracking motor has an approximately ten-to-one reduction ratio, while the vmotor' il 'has' an approximately one-to-one ratio. a

The function of thetracking motor i6 is to bring the turret or other load into operationfrom itsV positionof rest; whereupon, by suitableY ma nipulation of the control handle, the slewing motor ,il is brought into'operation vand its driving component. superimposed on that ofthe.-

tracking vmotor IS to permit` the load to be brought at comparatively Ahigh speedl to approxi mately its desired nalposition.- At that point, the last fine adjustment isbrought, about by,- returning the control substantially to the tracking motor.

A more precise `conceptionof: the foregoing, and a more exact appreciationof 'how these two motors co-act, canperhaps v:bestr be yobtained by referencev to the graph constitutingFigure 3. Thereinloutput shaft speed-is plottedas a func-V tion of the flow of energizing oil from the-Gerotor pump ill. The units employed'are of no-con sequence so long asv-they remain 1 constantA for the two functions. Twocomponent .curves are plotted, marked respectively tracking motor. and

'slewing'moton and a resultant curve is compounded from these two component curves. At restror Zero position, indicated at 8, andcorresponding to'thef'neutral position ofv control handle iSA of the camshaft. l l, no oil flow takes` place from the Gerctor` i4 tothe motors I6 rand il and these latter are at rest. i4 is by-passedY directly back lto reservoir I3.

If now the control handlel isswung through a small angle from its rest position in either direc.- tion (and the curves are valid for either direction of motor rotation) someoil'passes from curve in Figure 3, cam' 5I does notlift the piston valve; osecondary metering valve 46,- all Yas later will loe-described. Asa result,- ow of working oil issolely to thetracking motorv Iii.. Thiscor- Irespondsv to the intermediaterportion i--A-on the` resultant curve.Y Thus, through the .positions E-.AB-thelresultant curve andthe tracking. motor curves are identical. i Oilv fromrtheiGerotor |4-,Which; does; not reach .the motor ,l 6 during..tlfiis,v -stage vof thcV operatipns` is returned `through suitw Oil from Grerotor able channels to the reservoir I3. While it has been suggested that -A in Figure 3 corresponds to'a throttle opening of approximately 3 in the particular case undergoing description, more generally it might well constitute any intermediate throttle position.

As has been said, during this time oil is supplied only to the tracking motor I5. This latter operates at intermediate speed and intermediate torque. The motors l5 and I'I are geared to a common output shaft, in a manner constituting the subject matter of my said co-pending application. The details of this gearing do not per se form part of this invention, and are therefore omitted from this application.

Although oil is supplied only to tracking motor I5, throughout the range from -B on the resultant curve in FigureS, more and more oil passes the control unit as control throttle IBA is brought further from kits restposition, until the motor I6 is brought up to its maximum energy at B with full output from Gerotor pump I4 tothis motor. This corresponds to slow speed operation of the motor unit at maximum torque. It further corresponds in a typical instance to an approximately throw of the control handle IBA. Thus operating handle ISA is swung to permit increased oil ow when higher motor torque is required to compensate for increased load. Position B corresponds to the maximumv load which can be handled by the motor assembly. l

When it is desired to compound the action of the slewing motor I'I on that of the tracking motor I3, the control handle I8A is thrown still further in the desired direction. The control mechanism within the casing I0 then diverts in a manner which will be described, some orf the oil pressured by the Gerotor pump I4, from the motor I to the motor Il.

It will be noted from the characteristic curve of the tracking motor I6 as shown in Figure 3 that while the rst portion of this curve from I) to B corresponds to the resultant curve, from point B on it displays a falling gradient. This is due to the fact that as more and more oil is supplied to the-slewing motor I'I, tracking motor I6 becomes progressively starved of energizing fluid. i

The slewing motor Il, which comes into action at B, Figure 3, displays a steeply rising gradient. The output shaft speed thereupon rises sharply,

due to the increased effect of the component of A driving energy of the slewing motor upon increase in input fluid to that motor.

A torque curve would correspond roughly to the tracking motor curve, with maximum torque at B and with drooping characteristics beyond. By properly choosing the throttle setting, an output shaft speed can be selected which will provide optimum results for a particular load condition.

These` characteristic curves of the two motors, properly identified in Figure 3, are algebraically superposed in the manner already suggested to produce the resultant curve characterizing the action of the motor unit. Consideration of this curve discloses that since oil flow from Gerotor I4 is a maximum at point B and cannot thereafter increase, then as the handle IBA is moved more and more to increase thediversion of oil to thefslewing motor il, necessarily less` and less oil passes to motor |6. Finally a point is reached where substantially all of the oil is diverted from this motonand the motor I6 is 6, carried substantially as an idler. When this condition is reached, the drive takes place substantially entirely through the one-to-one ratio of the slewing motor. The load is carried at the highest possible speed, but with relatively low torque.

Returning now to a discussion of the details` of the control system, as illustrated in Figure z 1, within the casing I0, I provide a primary camcontrolled metering valve I9. -This valve comprises a valve housing 20, generally cylindrical in contour, in which reciprocates piston valve 2|, made fast through a suitable opening in the bottom of the casing 20 to a piston rod 22. This piston rod 22 extends through a suitable sealing bushing (not shown) in the bottom of housing 20, and terminates at its outer extremity in cam follower 23 which engages and rides Yon the cam 24, made fast on the cam shaft II. part or skirt of the Valve element 2| is recessed transversely at 25 in the general shape of an inverted V. A coiled spring 26 of moderate pressure is disposed between the top surface of the piston valve 2| and the tcp of the casing 2|), and serves normally to bias the piston valve gently in a downward direction. When the cam shaft |I is in its neutral or rest position, the cam 24 is at its position of minimum throw. Spring 26 urges the pistn 2| downwardly so that the follower 23.

closely follows the cam 24. Portion 21 of inlet conduit I5 lets into the side of casing 20, the flow of pressure fluid therethrough, however, being normally blocked by the side walls of the piston valve 2|.

Also provided within the casing IU is a primary load-controlled relief valve indicated generally at 2'8. This valve 28 comprises a valve casing 29 and an inverted piston valve 30. Coiled spring 3| extends between the top 32 of casing 29 and the interior face 33 of the piston valve 30, the spring thus extending through the hollow skirt of the piston valve. This spring, along with the pressure of the metered fluid passing metering valve i9, exerts a downward force tending to bias the piston valve 33 towards the bottom of valve casing 29.

Keeping in mind that the Gerotor pump I4 is of the constant-speed, constant-output type, it will be seen that at al1 times when this pump is in operation there is a constant output of oil through the conduit I5. When this oil is blocked in portion 2'| by the piston valve 2| it chooses Whatever path is available. It passes through nipple 34 into the space 35 formed between the bottom of casing 29 and the working face 33 of/ piston valve 30. The pressure of the liquid passing through nipple 34 is sufficient to overcome the resistance of spring 3| and to maintain open the branched outlet pipe 3B which lets into valve casing 29 near the bottom thereof. At this time,

the entire output of pump I4 flows from the outlet pipe 36 without appreciable resistance, through the main outlet pipe 31, to the reser- Voir I3.

If now, however, handle I8 be rotated a slight distance in either direction following the practice already developed in the discussion of the graph of Figure 3, say through an approximately 3 throw, the cam 24 is rocked so as to force the piston rod 22 of the metering valve I9 upwardly for a slight extent. The piston valve 2| is thereupon moved upwardly through a limited travel, against the tension of spring 25. This travel is sufficient for the opening 25, at least near its small-volumeapex region, to come adjacent the portion 21 of the inlet pipe I5. Partof the con- The bottom stant flow ofoilffromiGerotor I4 will'pass through.

inletr/pipe I rand'portion; 21,:toandthrough lcontinuation A38=rof theiinlet .pipes .disposed on theA opposite-side of the metering valve 26'... Part of this pressure'fluid whichA courses the metering valve 28 passes upwardly from inlet pipe through ybranch'pipe 3S and lets into the top of the. relief valve 2S, above the Ypistonvalve i3d, exerting pressure thereon; The force of thispressurexfluid'is superposecl on that exerted by the spring 3 I; Since. the pressure of this iiuid on the top of valve 3l) tends to .counterbalance that exerted bytheiluid comingthrough:branch pipe' 34 to the other facev of this piston, the forcezof the .springl is sufcient toxrnove the piston valvev Sdpdownwardly.' to a certainextent,` tending to block outletLpipe @d at least partly. and .under the control ofthe Working huid load. Flow betweenbranch pipes Stand. 'et isthereby. diniinished :in KVgraduated amount;

-A secondsecondary lcad-con`trcl relief valve is providedinthe'casing iii and is .indicated-gen.

through the small opening provided by the apex.

portion of the opening le in pistonvalve fi, for the initial setting'of'cam 2li.' Thatportion of 'the pressure fluid which is notirequired for energizing the system in the manner'now vto be described is snorted,y by means of primary relief valve through branch :pipes'dii and 'd to outlet'pipe Spring 3i of primary relief valve 2S' does not con.- pletely close outlet pipe 36 at this time. Under these partial-loadconditions fluid which under-- takes to traverse pipe 3S isfbloclced at this setting of Athe cam shaft l l which is undergoing descrip tion, .by a .second metering valve indicated generally at 46.

In a yrnannerexactly similar to Athat already de scribedwith respect to metering valve i9, cylindrical valve casing 41 is provided for this valve da.

which casing 41 houses a hollowl skirted piston valve I43, made fast to a piston rod t9.- This piston rod '49 terminatesl in a cam follower 63 rid-l ing on the cam: lI fast on'the cam shaft it'. A coiledispring 52 `extends between the top surface i3-ofthe valve casing lil and theA top surface f ofthe pistonvalve lit. An inverted V-shapod opening55 is provided intheV under portion of the skirt of the piston valve liti. Since the walls of the.` piston valveV 43 vblock the inlet pipe 38, the pressure iiuid can .flow only through branch .pipe 56 v`tothe. space providedk between the bottom of the casing 4I and bottom surface of the piston valve 42' of the secondary relief valve dii., From space Eil` this pressure .fluid ows through conduit 58 to a i-way valve 5d.:

These 4-way'valves' are well-known to the art andare `of conventional construction, .and ydo not per se form partof this invention. Accordingly, the constructional details of these valves will be omitted. It. is enoughto say that I prefer these 4-way valvesA to be. of' the. closed-center type,l

Wherebyzall passages therethrough are blocked when the cam shaft `II isn-in its neutral position.

One 4-Way Valveis associated with'eachof the two lal() motors, and .directs they pressure.`v fluid .tothelassoii ciated motorin fonedrection or. the other,zaccord'r ing tothe particularcam.setting;.to cause-rotation of the rnotor inthe Adesired direction. We

will assume that the-cam-.l on camshaftfH .is`

so set for the illustrated instance, -thatits associated cam follower GI and pistonrod B2 Vactuate the Ll-.way valve 59. inssuch `a manner'anddirection that flowV takesv place from conduit 5S, through valve 59, and conduitzi. to the left side of the trackingmotorui. Returnviiow is` from the tracking. motor Ilfthrough conduittll, i-way` valve 5S, branch conduit 65, and :return conduit 3l to the reservoir I3.`

As the handle' ISA isv swung vmoreand more from its rest or neutral-position, so thatfthe cam shaft II is rocked sthrough theA range of say between 39 and 10, the piston valve y2 I islift'ed more and 'more inthe casing 20 ofthe primary metering'valve I'9. In 'the meanwhile', throughout this entire rotation ofv cam shaft 'I I, Ithe opening 55 of the piston valve 48 remains closed against extension 38 of the inlet pipe. More and more pressure comes through pressure bleeder line 39 to the topside-of primary relief valve 28.7 The pistonA 3l' thereof finally is fully '.seated, thereby completelyblockingvoutlet pipe 3B.' All'of the constantfoutput oil'frorn Gerotor Iis utilized and is passed to the tracking motor I, so that the latter is operated at its high reduction lratio at full output-and with-highest degree of :torque:

Upon slight further movement of the control handle l 3A, opening 55 in the secondary metering valve Il? begins to open to the line 38.' Part ofthe fluid from this inlet ed courses across the secondary metering valve, andpressure isI exerted `from the branched pressure bleeder line 68 to the top of the seconda-ry relief valveI 40. Tending to counteract to a certain extent the pressure fluidfrom 38 and branch 5d,v the'combined pressure of the uid through-conduitt and'of the spring it forcesthe piston vvalve 42 slightly downwardly, blocking conduit 53 toa certain extent and-cutting off some of the flow through this `conduit from branch pipe 56. This diminishes slightly the flow-tothetracking motor I6. Simultane-4 ously, the fluid passing the secondary metering valve dii courses through'ccnduit 6l to the second i-way metering valve 68, which is associated with the slewing motor I'I. The mechanism of this valve da is operated through a piston rod 69- `through passage 38 of the-pressu-re` fluid is uninterrupted by this opening.

Full pressure from the Gerotor I4 is then imposed on the top'side of the relief valve'il, eventually causing the complete seating of this valve and the unloading of supply to the tracking motor I5, At this time, all

of the output of the pumpV il!v passes directly to the slewing motor l? which carriesthe entire load,

the motor it then being carried `simply as. anA

idler.

The-foregoing description has been made' on the.

assumption that the' handle lISA is thrown in but 9 a single direction. Should the handle ISA be thrown in the opposite direction, however, then the functioning of the primary and secondary metering valves and primary and secondary relief valves remains the same as has already been described. Proper directioning of the energizing fluid to the motors is accomplished solelybythe 4-way valves 59 and 68 and the cams' (illand 1I, which correspond respectively to these 'two valves, and which are so contoured that the two motors I6 and I1, when simultaneously iii-operation,` will always rotate in thesam'e direction. We4` have just assumed a clockwise directi'o'nfof rotation of the handle IBA, that is,4 to the-left in Figure l, so that the swing is to the rightinlFigure 2. We will now assume that the handle is thrown in the opposite direction, that is, to theright in Figure 1.

With this assumption, then with an approximately 3 throw, whereby flow takes place only through 4-way valve 59 from pressure conduit 58, then the flow of liquid may be traced through 4-way valve 59 down through conduit 64, through tracking motor I6, and back through conduit 63, 4-way valve 59, branch pipe 65, to return pipe 31. Upon further throw of the handle `ISA in the same direction, the circuits just traced remain vestablished but withslightly diminished llow so that the torque developed by the motor I6 drops ol slightly, while at the same ytime a slewingmotor circuit is established through conduit 61, 4-way valve G8, down through conduit 13, to slewing motor I1, back through conduit 12, 4- way valve 68, and back to return conduit 31. Finally, when the handle ISA is thrown through the full extent of its throw to the right, secondary relief Valve 4B discontinues flow tothe 4- way valve 59, and all of the output of the pump I4 passes through primary. and secondary' metering valves I9 and 46 to the 4-way valve 63, and thence through conduits-13 and 12, to and from the slewing motor I1. 'i Y Where desired, brake control of the motors-is had by way of valve 14. This is'actuated by cam 15 on shaft II and cam follower 16. It controls the pressure of conduit 1-1 applied to the motor by way of conduit 18. Y o' v While the construction has been shownfschematically and has spread out in development, it will f course be understood that in actual practice the unit is small, compact, and self-contained. It is extremely rugged and will perform satisfactorily under all extremes of operating conditions. My experience has shown that it is admirably equipped for tank turret control over the roughest terrain. Moreover, it is entirely suited for ship or aircraft turret control, or for general application where dual motors are required under widely dissimilar varyingload conditions. Constant output pumps of extremely simple design and inexpensive production can be employed admirably with but simple regulatory equipment for widely varying load conditions. I have found that a Gerotor pump developing about 50G-600 p. s. i. max. pressure will perform with entire satisfaction. Entirely suitable is the combination of a tracking motor with a -1 reduction ratio, operating at a maximum speed of about one-third that of a 1-1 ratio cooperating slewing motor. Wide acceptance in the art connotes and points tothe essential advan-` tages of my new construction.

As many possible embodiments may be made of my invention, and since many changes may be made in the embodiments hereinbefore set 10 forth, it will be understood that all matter described herein, or shown in the accompanying drawings, is to be interpreted as illustrative, and

-not in a limiting sense.

I claim as my invention:

1. `As an element of a hydraulic control system wherein constant current uni-directional pressure fluid is utilized to energize paired hydraulic motors, a control unit for said motors comprising -a manually-operated cam shaft and metering valves operating from said cam shaft, and connected with said motors and with said source of fluid supply so as, when the system is at rest, tc'return the entire fluid supply to a reservoir, and upon continued throw of the cam shaft, first to bring one motor into operation at full speed, and'thereupon to provide differential supply of the energizing fluid to the paired motors.

2. As part of a multiple-motored hydraulic system, a control unit comprising means providing a vconstant unit-volume of powering fluid, primary means for primarily metering a desired part of said powering fluid for transmission to the multiple motors, means for directing the remainder of said fluid back to a storage reservoir, secondary means for metering adesired part of the primary-metered fluid to one of said multiple motors, means for directing the remainder of said primary-metered fluid to the other motor, and means for regulating both said metering means.

3. As part of a multiple-motored hydraulic system, a control unit comprising means providing a constant unit volume of powering fluid, primary means for primarily metering a desired part of said powering fluid for transmission to the multiple motors, primary relief means for directing the remainder of said fluid back to a storage reservoir, secondary means for metering a' desired part of the primary-metered fluid lto one of said multiple motors, secondary relief means for directing the remainder of said primary-metered fluid to the other motor, lmeans for regulating both said metering means to control the admittance of fluid therethrough, and means forming part of each said relief means and connected with the cooperating metering means for adjusting the outflow through said relief means.

4. As part of a multiple-motored hydraulic system, a control unit comprising means providing a constant unit volume of powering fluid, primary means for primarily metering a desired part of said powering fluid for transmission to the multiple motors, means for directing the remainder of said fluid back to a storage reservoir, secondary means for metering a desired pari; of the primary meteredffluid to one of said multiple motors, means for directing the remainder of said primary-metered lluid to the other motor, and a single, manually-controlled means for regulating said metering means.

5. A control unit forming part of a multiplemotored hydraulic system, comprising, in combination, a source of constant-volume energizing fluid for operating said motors, regulatable primary metering means for directing a desired part of said energizing fluid to said motors, an associated primary relief means for by-passing the unused energizing iluid back to a system reservoir, a secondary regulatable metering means for directing 'a desired part lof the primary fluid to one said motor, secondary relief means associated with said last-mentioned means for directing the remainder of the primary metered fluid to the other said motor, and means connected one with each said secondary means for respectively controlling/.trie direction Vof fluid suppiyto each said motor.

.6. .A control unit forming. part 'ofi'. aV multiple- Inotored hydraulic systemcomprisinggiin combimary meteringmeans zfor directing a. desiredpart ofsaid fenergizngiluid tors'aid motors, an associatediprifmary 'relief means for. ley-passing ,tliei un usedenergizing iiuidv back toA asystem reservoir, a .f

.secondary regulatable metering-means'for direct- ;ingragid'esired part ,of the.v primary uid to one'said motor; Asecondary. reliefmeans associated vWith .saidvla'st-mentioned metering means for directing thearemainder. `of the primary-metered fluid tother othersaid motor, .means connected one with each saidsecondary means forrespectively controlling the directionf of fluid supply Vto each said motor, andmeans for regulating said meteringmeans and said direction-determining means.

' 7. Acontrolunit-forming-part of a multiplemotored hydraulic system, comprising, incombination, a :source viof constarit-Vol-ume4 Lenergizing fluid foroperating said motor, regu-lat'able.` primary meteringfmeans for directing. a desiredpart of saidnenergizingiiuidto said motors,l aniassociatedfprimary relief means for bypassingthe unused venergizing fluid backto a system reservoir, asecondary kfregulatalole metering means fondirecting a desired part ofthe primary fluid ,toene said motonsecondary relief means., associated With said last-mentioned metering means V`for directing'the remainder of the primary-metered fluid to the other said motor, means connected one:with each-said secondary means. for-respec- -tivelycontrolling the directionof uid-supplyto each said motor, and manually-operatedmeans common to, andv for regulating said,.metering means and said direction-determining I means.

.i 8.--A,contr.o1 unit-forming part of. a multiple-` motoredvhydraulic system; -comprisingin combination, meansfor supplying a-constant unitoutputoienergizing liquid, aregulatable primaryl metering valve ,forpassing a desired part oisaid .en-

er-gizing liquid-to'=saidvmotors, aprimary load-adiusted relief fvalve .for bypassing Ythe; energizing fluid. frejectedzyby said. primary.V metering r4.valve backrto-asystem reservoir, a 4regulat alole second- Yaryrmetering, valve fors-:metering a desired part oiztheaprimarymetered fluid to,V one said motor, -aisecondary'loadhadjustedsrelief'valve for directing ithe. 'remainder'fofzsaidf primaryfrnetered. fluid itoztheiotherzsaidimotor, and 4Way valves in cirf :ouit;.;one:;-with eachisaidsecondary meansjor de ',termining'rthefdirectionof flown the energizing liquidita. eachssaid motor.

wAnccntrolsunit `lrorming part of a fmultiple.-

umotorecl1hydraulicsystem,y comprising, in combi- :natiomtmeansfor supplying aconstant unit out- :putz of1::.energizing liquid,` a` yregulatalele; primary :metering .valve :,iorlpassing; ai desired `partof Vsaid energizingliquidatojsaid motors, ay primary loadadjusted reli'ef rvalve for ley-passing the energizin g fluidfi'ejected liiyrs'aidi primary :metering valve, Va

secondaryf meteringivalve. for `metering a desired part 'of the primary-metered uid to .one-said motor,y a secondaryy load-adjusted relier'v valve for directingthefremainder of said primary-metered uidrtofthef-other-said motor, Ll.-Way Valves in circuit,one.with each said Ysecondary means, for `deter-mim'ngthe directionof flow of the energizing-:liquidtoieaehsaidmotor, a cam follower on 4each said-metering, valve=and each said Li-Way Valve, afmanually-,operated camshaft, and cams .en said cam-shaftcooperating Witlreach said cam follower; ).for fr egulating the corresponding Valves.

ALBERT RIVINGTON STONE.

.REFERENGES- ACITED 'Ifhe following'lreferencesare of record in the file :fof this patent 'UNITED STATES PATENTS 

